The present invention relates to a drive for adjusting the inclination of a backrest component of a seat in general, and particularly to a motor drive suited for use in vehicle seats.
There are already known various constructions of hinge arrangements which tiltably mount the backrest component on the seat component of the respective seat. It is also already known to incorporate tilting mechanisms into the hinge arrangements, which tilting mechanisms then adjust the inclination of the respective backrest component of the seat and hold the backrest component in its adjusted position. Then, it is also already known to utilize a motor for actuating the tilting mechanism, and to interpose a transmission between the motor and the tilting mechanism.
An example of a conventional backrest inclination adjusting arrangement of this type has been disclosed, for instance, in the German patent DT-PS 1,630,907 where a motor drive is being used for the adjustment of the angular position of the hinge member of the hinge arrangement which is connected with the backrest component of the seat. The motor drive revealed therein includes an electric motor and a reduction gear transmission interposed between the electric motor and the tilting device and which constitutes a structural unit with the electric motor. Inasmuch as it is desired that the tilting mechanism of the hinge arrangement be also manually actuatable by operating a handgrip when the electromotor becomes inoperative, the abovementioned reduction gear transmission can only be a spur gear transmission which can be jointly rotated when the handgrip is rotated, provided that a switching coupling, which requires the availability of additional space for its provision, is to be avoided. The spur gear reduction transmissions of this type assume, because of the necessarily great reduction ratio and the multitude of reduction stages which have to be provided in order to achieve the above-mentioned huge transmission ratio, a space in the vicinity of the hinge arrangement which has a relatively huge volume. For this reason, it is usually impossible to arrange the driving motor immediately at the hinge arrangement inasmuch as the required space is not available there. Thus, it is usually necessary to arrange the driving motor at such a location where the necessary space is readily available. When this expedient is resorted to, the connection between the driving motor, on the one hand, and the hinge arrangement, on the other hand, is established by flexible shafts or the like. Even though it is already possible to achieve a satisfactory performance of the backrest component inclination adjusting operation with respect to the adjusting torques and adjusting speeds by resorting to the use of the conventional motor drives of this type, there still exists the pronounced disadvantage that the dimensions of the reduction gear transmission are considerable, especially when high-speed electric motors are being used, as a result of the necessarily high transmission ratios. Under these circumstances, there is, as a rule, required a complex construction of the transmission which calls for expensive special driving trains. When a hinge arrangement is used at both sides of the seat, an additional problem is encountered which resides in the fact that, when the driving motor is assymetrically arranged, it is nevertheless to be assured that the flexible shafts have the same length in order to avoid precession or recession of one of the hinge arrangements with respect to the other hinge arrangement.